1. Field of the Invention
The present invention relates generally to ultrasonic medical instrumentation, and more particularly, to methods and instrumentation for creating and sensing thermal lesion formation with ultrasound and/or radio frequency energy.
2. Prior Art
Ultrasonic and radio frequency (RF) instruments are well known in the medical arts. Such instrumentation may be used to make lesions in tissue. The operation of most available treatment systems is based on a fixed procedure time, that is the ultrasonic or RF energy is applied to the tissue for a predetermined period of time. Typically, the predetermined period of time is based on the worst-case scenario in order to ensure treatment efficacy. Under this method, tissue may be over ablated and peripheral thermal damage is prevalent and undesirable.
There are systems known in the art that measure the electrical impedance of the tissue to determine the efficacy of the lesion created. However, such a method has been found to be applicable only for select treatment modalities. Still other systems utilize a functional testing of the lesion (e.g., pacing and sensing across the lesion). However, such methods have been found to misrepresent how efficacious the lesion is. For instance, the functional signal may be blocked by something other than the lesion.